1. Field of the Invention
The present invention relates to stabilizer systems comprising at least one perchlorate salt and at least one polyalkylene glycol. More particularly, the present invention relates to the thermal stabilization of halogen-containing polymers, especially polyvinyl chloride (PVC) with compositions containing polyalkylene glycols and perchlorates.
2. Description of Related Art
Thermal stabilizers used for PVC may contain lead, barium, cadmium, tin, calcium or zinc compounds. Owing to environmental concerns, there is strong interest in eliminating these metals from PVC compounds and replacing them with organic based chemicals. Several organic based stabilizers have been proposed. However, their lower efficiency in PVC stabilization when compared to mixed metal stabilizers and/or their high cost presents a significant problem.
Calcium/zinc stabilizers have lower toxicity when compared to lead, cadmium and barium stabilizers. A method for preparing a Ca intermediate that can be used in Ca/Zn or Ca/Mg stabilizers has been disclosed in U.S. patent application Ser. No. 10/190,130, filed Jul. 3, 2002.
Lee et al, Polymer (Korea) 19(5), 543-50 (1995), and 18(6), 1021-9 (1994) disclosed the use of poly(ethylene glycol) PEG 400 or polypropylene glycol used together with epoxidized soybean oil (ESO) and Zn/Ca stearate for stabilizing PVC.
U.S. Pat. No. 6,348,517 discloses the use of the combination of polyethylene and polypropylene glycols and their esters, such as adipate and dibenzoate, as well as their ethers, with mixed Zn/Ca salts of fatty acids for stabilizing PVC against ionizing radiation during sterilization.
JP 50024388 discloses the combination of ethylene glycol (0.1 phr) in H2O/CCl4 with 2 phr Ca/Zn stearate and ESO for PVC stabilization.
JP 56055445 discloses polyethylene glycol and/or polyethylene glycol-polypropylene glycol block copolymer and a βπ-diketone as stabilizers for PVC.
U.K. Patent No. 1151108 discloses the use of dipropyleneglycol and other high boiling polyols, such as pentaerythritol and dipentaerythritol, for light stabilization of PVC.
FR 1211814 discloses the use of glycerol or propylene glycol mixed with Ca stearate or Na2CO3 for stabilizing PVC involving contact with foods.
Metal stabilizers have also been replaced by organic based stabilizer (OBS) See Modern Plastics, May 2001 and U.S. Pat. No. 6,194,494.
WO 02/48249 A2 discloses the use of amine/perchlorate system.
Other patents include U.S. Pat. No. 5,543,449, stabilization using a perchlorate and a terminal epoxide compound, and U.S. Pat. No. 5,519,077, on the use of perchlorate, a terminal epoxide compound, and an antioxidant.